The present invention relates to a method for the determination of the direction to a signal source.
The invention also relates to a device for the determination of the direction to a signal source.
In the field of surveillance it is important to quickly discover and classify the observations made. Signal surveillance is such an example where there is both a civilian and a military use. Such a use is to discover new signal sources. In this context signal sources are meant to comprise high frequency transmitters such as transmitting radar stations, radio transmitters of different types, jamming transmitters, etc.
The signal sources can geographically be situated anywhere in relation to the detection device. This prohibits the antenna of the detection device from having any specific directivity. Often, antennas with lateral beam widths of 90.degree. or more are used. Also the vertical beam widths are large, often several tens of degrees. The antenna amplification and therefore also the sensitivity of the device become lower than for a device with an antenna with greater directivity. In most cases this means that signal sources are only detected when their signals are directed towards the detection device. As the signal sources also emit signals within very large frequency bands, it is required that the detection devices have very large bandwidths. The limited angular resolution and limited sensitivity in combination with the large bandwidth make detection devices of this type more to be considered as a warning device--they can indicate that a signal source exists but not where it is or in what direction it is.
Passive, non transmitting radar stations have been used for signal detection within the frequency range utilised by radar. The narrow beam of the antenna in a radar, that can be used as an accurate direction determiner, also results in that the antenna amplification is large enough so that even signal sources at large distances can be detected and this even if the beam of the antenna of the signal source (main beam) is not directed towards the detection device.
The problem with utilising a radar with a narrow antenna beam is that its antenna, to be able to cover a large angular area, has to conduct an extensive and therefor time consuming search procedure, especially in those cases when nothing is known about the direction or if there is a signal source at all.
It is also known to combine detection devices of the warning type and radar stations for a more accurate determination of the signal source. These solutions to the problem have had a limited usability because of deficiencies in the timely accordance of the measurement. The radar has in these cases not been able to determine if a detected signal source is the one intended by the warning device. The probability of the main beam of the signal source being directed towards the warning device at the same time as the radar station is directed towards the signal source is very small. The object of the present invention is thus to provide a method and a device for the determination of the direction of a signal source through co-operation between detection equipment of the warning type and a directional determining detection device such as a passive radar, in such a way as to eliminate the above-mentioned deficiencies such as i.a. the timely accordance of the measurement of a signal source, of earlier used methods.